Generally, multi-part dental implant systems are used in dental surgery to reconstruct dental parts of a human being. Usually, multi-part implant systems are comprised of a dental implant, preferably a dental implant screw, which is inserted by screwing or pressing into a receiving bore which has been prepared e.g. in the bone tissue and abutments or secondary parts adapted, inter alia, to support a dental prosthesis.
A frequent problem arising with the above described multi-part dental implant systems is the correct positioning of the abutment or the secondary part within the dental implant already placed in the bone tissue.
The problem of the correct positioning was addressed by numerous prior art patent publications.
In particular, according to U.S. Pat. No. 5,195,852, a cylindrical cavity was devised, at the coronal end of the dental implant screw, to include a plurality of striations for preventing the rotation of the abutment supporting a prosthetic structure. However, as the striations were provided right at the upper end surface of the dental implant screw, the stability and sterility of the coupling between the abutment and the dental implant screw was unsatisfactory.
Another solution was proposed by U.S. Pat. No. 5,281,140 wherein a three part dental implant system comprised of a dental implant, a first intermediate abutment part and a second distal abutment part was disclosed. The dental implant was provided at the coronal end thereof with a chamfered shoulder, followed by a hexagonal opening extending apically into the dental implant and followed further apically by an internally-threaded cylindrical-shaped passage adapted to receive a fastener screw. The first intermediate abutment part was shaped at the apical end thereof complementary to the chamfered shoulder and the hexagonal opening of the dental implant, respectively, and provided with a multi-sided projection at its side facing the second distal abutment part. Further, the second distal abutment part was shaped at an apical end thereof with a cavity complementary to the multi-sided projection of the first intermediate abutment part, such as to provide for the relative rotational positioning of the two abutments when coupled via the fastener screw to the dental implant.
Nonetheless, the solution of U.S. Pat. No. 5,281,140 was also not free of shortcomings due to the larger number of parts involved. Also the relatively large taper degree of the chamfered shoulder was not suitable to provide for a sufficiently stable and sterile coupling of the abutment parts to the dental implant.
EP-A-475 299 discloses a dental implant screw which is connectable to a two part abutment, wherein the dental implant is provided with centering and positive lock means spaced from its shoulder and wherein a short cylindrical recess extends between the centering means and the shoulder. EP-A-475 299, however, also fails to provide for a sufficiently stable and sterile coupling of the abutment parts to the dental implant screw.